TMS320F280049C: Access reserved GPIO

Johnny Chen

Part Number: TMS320F280049C

Hi Champ,

I am asking for my customer.

May I confirm that the reserved field in GPIOB (GPIO 36 & 38) if it is written in 0 / 1 (access the pin), will it cause the MCU any problem ?

The customer prefers to access the GPIO32 ~ 39 as a byte at a time. Unfortunately, there are two reserved field in it.

They are facing a problem when debugging the code, it will stops at here.

As the TRM page. 869 Caution mentions it isn't allow to implement like this. Am I correct ?

Also, the customer would like to keep the same setting for the GPIOA and GPIOB in programming, access the GPIOs as a byte in one time.

They would not like to set GPIO32 ~ 39(except 36&38) one in a one time. Not only it keeps the code neat, also narrows down the code size.

Any suggestion to avoid of this or any ways for doing their wishing ?

Thanks for any help. Thanks !

BR, Johnny

over 4 years ago

+1 Nima Eskandari over 4 years ago

TI__Guru 52040 points

Please do not write to any reserved bits. There could be internal TI only connections in there causing issues.

If there are unbound GPIOs, they could still be used in the application.

Check the reserved value, if it's 0, continue to do your full byte access but write 0 to that bit. If it's a 1 make sure your byte access writes a 1.

Nima

0 Johnny Chen over 3 years ago in reply to Nima Eskandari

TI__Expert 4980 points

Hi Nina,

May I make sure that it also happen on F28002x and F28003x, correct ?

Thanks.

0 Nima Eskandari over 3 years ago in reply to Johnny Chen

TI__Guru 52040 points

That's correct!

0 Johnny Chen over 3 years ago in reply to Nima Eskandari

TI__Expert 4980 points

Hi Nima,

Thanks for your reply.

I am asking for this is because the customer is questioning the reserved bits in GPIO.

Below is the snapshot from TRM, the two reserved bits are suppose to be GPIO36 & GPIO38.

According to your explanation, these two reserved bits are for internal TI connections used.

However, the customer seems it is a DSP HW bug, and ask do we have one IC HW plan to fix it.

I believe it isn't a problem based on your reply. May I have your comment on the customer's thought ?

Thanks.

0 Nima Eskandari over 3 years ago in reply to Johnny Chen

TI__Guru 52040 points

Are GPIO36 and GPIO38 available in the GPIO PINMUX in the DATASHEET?

0 Nima Eskandari over 3 years ago in reply to Nima Eskandari

TI__Guru 52040 points

GPIO36 and GPIO38 are not available. Leave those values as ZEROs.

0 Johnny Chen over 3 years ago in reply to Nima Eskandari

TI__Expert 4980 points

Hi Nima,

Thanks, I am clear your saying. This statement is standing on our side to explain to customers.

If the user really accidentally writes these reserved bits as ONEs, does it have no effect on all aspects of the MCU ?

However, the customer would like to get a guarantee from TI. It is guaranteed to the competitors from getting feedback from customers.

May I have your help to check all the reserved bit like GPIO36, GPIO38 and GPIO60~63, although there are no real GPIOs at all in fact ?

Furthermore, the GPIO36 and GPIO38 currently intersperse in the middle of GPIO PINMUX, in response to this matter from the customer, would TI have any preventive mechanism or action of moving these two bits to the back in the future design ?

Thanks for your help. I appreciate it.

0 Nima Eskandari over 3 years ago in reply to Johnny Chen

TI__Guru 52040 points

Jason Whiles Can we guarantee this?

+1 Jason Whiles over 3 years ago in reply to Nima Eskandari

TI__Expert 5450 points

Johnny,

We can't make a blanket statement about Reserved registers/fields throughout the TRM. Some of these may have effects on the device and should not be written.

However, I can confirm for the empty or non-existent GPIOs in the GPIO registers, these are unimplemented registers. Writing to them will have no unexpected impact on the device.

Best regards,
Jason

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F280049C: Access reserved GPIO